(CNN) -- A former Los Angeles police officer who police say has violently threatened his former colleagues shot at least two officers early Thursday, killing one, sparking a huge manhunt in Southern California, according to authorities.
Christopher Jordan Dorner, 33, is also wanted in a double slaying Sunday in Irvine, California.
The California Highway Patrol issued an alert Thursday morning urging officers in several Southern California counties to be on the lookout for Dorner after the overnight shootings.
Two officers in Riverside were shot, one fatally, police there confirmed to CNN. CNN affiliate KTLA reported another officer was shot in Corona, California.
Irvine police identified Dorner on Wednesday as the suspect in the February 3 deaths of Keith Lawrence and Monica Quan in Irvine.
Dorner also has made violent threats against other Los Angeles police officers, the agency said Wednesday.
"I will bring unconventional and asymmetrical warfare to those in LAPD uniform whether on or off duty," Dorner allegedly wrote in a lengthy letter promising retribution against the department, where he worked from 2005 until 2008. An LAPD source provided the document to CNN.
The letter writer claimed he was terminated for reporting excessive force by a fellow officer, and said his attacks were retribution for his termination, as well as a culture of racism and violence he says continues within the department.
He called the attacks against police "a necessary evil that I do not enjoy but must partake and complete for substantial change to occur within the LAPD and reclaim my name."
Los Angeles police warned people who encounter Dorner not to approach him, saying he is likely "armed and extremely dangerous."
"Our department is implementing all measures possible to ensure the safety of our LAPD personnel, their families and the Los Angeles community, and will continue to do so until Dorner is apprehended and all threats have been abated," police said in a statement.
CNN's Mallory Simon and Deanna Hackney contributed to this report.

Probably. This all started with some n00b douche lying about me. I guess I could have let it go, but that's just not my nature. Then a couple of more idiots joined in, and BOOM there it is. I rarely start these things. I just don't suffer liars, douches and fools.

Yeah, and I'm sure you never did anything to anybody to make them dislike you. Poor widdle native, just the nicest widdle guy in the whole world and all those mean ol white people keep picking on him. There's nothing you won't stoop to and to deny it is the height of hypocrisy.

As for the rest, your whole persona here is a miserable, sniping, envious bitch. The closest you come to friendship is finding a like-minded douche and joining a pile-on (BUT IT'S DIFFERENT IN REAL LIFE, RIGHT? ). I realize that it burns your ass that people like me and think you're a piece of shit, but that's not really my fault. If you didn't keep taking potshots at me, I wouldn't give your bitch ass a second thought. Hell, I even ignored one from earlier in the week. I guess that really upset you. Sorry about that.

And I'm also sorry your old lady would have to turn 20 tricks to afford the work I had done to one of my pistols today, but again, your poor choices have nothing to do with me.

Back to your usual Chiefsplanet bravado. It's pathetic that you go back to your popularity on this board. It's a ****ing message board.

Also, you're not very good at arm chair psychology. You like to invent what you think people feel. I take potshots at you because it's so easy to rile you up. When I have time to waste, I know all I have to do is send a few posts your way and you go off the deep end again.

Probably. This all started with some n00b douche lying about me. I guess I could have let it go, but that's just not my nature. Then a couple of more idiots joined in, and BOOM there it is. I rarely start these things. I just don't suffer liars, douches and fools.

You are so full of shit. You live for these little "confrontations" so you can justify being a reincarnated Skip Towne.

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Look﻿ at your﻿﻿ comment, now back to mine, now back at your﻿ comment, now back to mine. Sadly it isn't mine, but if you stopped trolling﻿ and started posting﻿ legitimate comments it could look like﻿﻿ it's mine. Look down, back up, where are you? You're scrolling through comments, writing the﻿ comment your﻿ comment﻿ could look like. What did you post? Back at mine, its﻿﻿ a﻿ reply saying something you want to hear. The﻿﻿ reply is now DIAMONDS. Anything is possible﻿ when you think before you post.

Back to your usual Chiefsplanet bravado. It's pathetic that you go back to your popularity on this board. It's a ****ing message board.

Also, you're not very good at arm chair psychology. You like to invent what you think people feel. I take potshots at you because it's so easy to rile you up. When I have time to waste, I know all I have to do is send a few posts your way and you go off the deep end again.

Now, keep dancing bitch. I didn't say you could stop.

So, I never interact with or mention you unless you snipe me, and by your own admission, you snipe me hoping I'll respond to it, but I'm the one who's obsessed? You repeatedly cry about it being only a message board..... on a message board? Nothing that happens here matters, yet you squeal like a little girl over rep comments. Did you wake up from some sweaty dream about me and feel compelled to fire off another barrage at 3:00 in the morning?